This invention relates to fasteners of the type utilized to secure removable modules or partitions to a receiving structure known as "jacking screws".
One specific application of a fastener of the type of the present invention is to secure drawers or modules containing electronic components into a cabinet or frame.
Another application for the present invention may be in the mounting of removable covers, access panels, drawers, inspection plates and the like to electrical, mechanical or hydraulic apparatus.
It may be realized in such installations that repeated fastening and unfastening of the jacking screw may be necessary in the servicing of the structure apparatus into which the fastener is disposed. Accordingly, in meeting one of the requirements of the present invention, it is necessary for a fastener of the type described to withstand repeated installations and removals without deterioration either of the fastener or the structure into which it is disposed.
In the case of threaded fasteners of which the present invention is included, the fastener must be disposed within the mounting device in which it is contained in such a manner as to permit relatively free rotary motion with respect to such mounting device as to allow relatively free insertion into the structure to which the mounting device is ultimately attached.
The illustrated embodiment of the present invention is in a jacking screw for electronic modules such as drawers occurring in scientific and medical instruments, which drawers often contain plug-in electrical connectors which are required to be firmly connected to their mating receptacles or plugs in instrument cabinets. Thus, it is necessary for the jacking screws to cause the modules or drawer to firmly seat in a cabinet, insuring proper alignment and contact of mating connecting members.
Illustrated in FIG. 1 and labeled "Prior Art" is a fastening device known and previously used for jacking screw installations. At least in some applications, the illustrated fasteners are not of sufficient heavy-duty construction for repeated heavy usage, as where the drawer or module being jacked in and out is either heavy or offers severe resistance to translational motion. In such instances, the head portion of the threaded fastener tends to back out of the retaining collar, destroying the jacking capabilities of the fastener; or it strips the collar completely from the mounting panel.
With the illustrated prior art jacking screw, it has been observed that during installation of the collar and fastener into the mounting device, the threaded fastener itself may be effectively captured by the collar mechanism such that relative rotary motion therebetween becomes difficult, if not impossible. It should be readily recognized that this undesirable aspect of the device available in the art can cause accelerated deterioration of the device as by imposing additional stresses upon the collar or threaded fastener portion, eventually leading to its pulling out of the mounting device, releasing the jacking screw or deterioration of the threaded fastener, e.g. head deterioration.
The present invention overcomes the problems exhibited by these prior art fasteners. The head portion of the threaded fastener is fully open such that it may be driven by either conventional screw driver mechanisms (blade or phillips head) or the head may be formed in conventional bolt-head (hex or other conventional pattern) construction. In the present invention, the fastener is captured into the collar portion by means of a compression or swagging technique which causes material of the collar to cold flow into special structure including grooves in the fastener providing a strong, yet flexible fit. The location of the groove is such that the bearing or frictional surfaces of the fastener and the collar permit, or, even promote relative rotary motion between the threaded portion of the fastener and the retaining collar. These and other features of the invention will be apparent from the following specification and claims.